Solar panels and other kinds of energy sources produce variable voltages, which, depending on the type of panel, may range anywhere from 10 to 100 volts (or even higher in some instances). It is known to the inventors that there are efforts to combine solar panels with a high-voltage bus (e.g., in the 200 to 600 volt range), which may be implemented via step-up converters that have an output voltage larger than its input voltage.
A discussion of some current DC-to-DC converter topologies can be found on the web site http://www.boostbuck.com/, which includes discussions of boost-buck switching converter, Cuk Converter, Coupled Inductor Cuk Converter, and Integrated Magnetics Cuk Converter. Other topologies for direct current voltage conversion include boost converter, buck converter, flyback converter, etc.
A boost converter typically includes at least two switches, such as a diode and a transistor, and at least one energy storage element, such as an inductor. The transistor is used to periodically connect the energy source directly to the energy storage element to store energy into the energy storage element; and the energy storage element causes the converter to output a voltage higher than its input DC voltage. Filters made of capacitors can be added to the output of the converter to reduce changes in its output voltage. The diode prevents the electric current in the output from flowing backwards.
However, one of the problems with existing direct current to direct current (DC-to-DC) converters is that in some cases their low efficiency may erase a good part of the gains made by using a high-voltage bus.
In a prior high-voltage system bus known to the inventors, inverters connected to photovoltaic systems operate in a wide input voltage range, such as between 250V to 600V or between 300V to 1000V, allowing for variations of the solar energy available and the resulting voltage swings. Operating a DC-to-AC inverter over such a wide range of input voltage reduces its efficiency and increases its cost.